The protestors included members of international and British environmental and social-rights groups, including the Gaia Foundation, London Mining Network, War on Want, Divest London, Global Justice Now, and Stop Mad Mining, among others.

These investments are having many impacts. For one thing, they are providing an economic impetus for a stampede of road and infrastructure expansion. At present, there are plans for 29 massive "development corridors" -- almost all prompted by mining investments -- that will open up huge swaths of wild and semi-wild areas to a range of new human pressures, such as poaching, logging, and habitat destruction.

"Development corridors" driven by mining could open up Africa to massive exploitation.

Large foreign investments can also fuel inflation. A few become fabulously rich from big mining projects but many others are left behind -- and often struggle just to put food on the table or pay their rent.

Beyond this, many have questioned the value of so-called "Corporate Social Responsibility" investments by mining corporations, claiming they are little more than greenwashing designed to make the corporation look good but often have few real benefits for local communities.

According to Hannibal Rhoades from the Gaia Foundation, one of the organizers of the protest, "Foreign investors can smell blood in the water in Africa right now. They're after quick profits but we see huge long-term risks to Africa's natural wonders and native societies if this feeding frenzy isn't brought under control."